There is known, for example from U.S. Pat. No. 5,547,618, a method for manufacturing optical lenses comprising the following steps.
First, a mould assembly 10 (or molding assembly) is assembled, comprising two moulds 12, 14 (or mould shells) and a gasket 16 (or sealing member). The mould assembly thus defines a molding cavity 18.
Thus, in the present description, a mould is one hollow part of the mould assembly, which forms with the gasket and eventually another mould the moulding cavity.
Next, the cavity 18 in the mould assembly 10 is filled with molding material. Conventionally this is done by pouring the molding material into the molding cavity through an opening 20 provided for this purpose in the gasket 16 at the periphery of the moulds 12, 14.
Then, the molding material is polymerized.
It is known in this kind of process to define the surface of at least one mould using an optimization process so as to ensure that the surface of the optical lens has desired optical properties. The inputs to this optimization process are geometrical properties of the surface and/or optical properties of the optical lens to be molded and the areas of the surface where these optical properties must be satisfied.
Nevertheless, using such an optimization process may lead to very complex surfaces. In particular, as shown in FIG. 3, the edge 22 of the surface 24 of the mould 12 defining a cavity may have irregular shapes. In particular, this edge 22 may present waves and/or be uneven. As a consequence, manufacture of a gasket 16 adapted to the mould 12—i.e. adapted to ensure sealing of the cavity 18 during the molding process—is very complex. Indeed the shape of the gasket 16 must be adapted to the edge 22 to ensure sealing of the cavity 18.
Moreover, the surface 24 of the mould is defined by an optimization process for each type of optical lens. Thus the edge 22 of the surface 24 is different for each mould 12 defined this way. Consequently a special gasket must be produced for each optical lens. This leads to a great number of different gaskets and thus induces significant costs.